Boffins take the temperature of the cosmos

The universe is cold and getting colder, according to work by an international team of scientists working with CSIRO’s Australia Telescope Compact Array near the NSW town of Narrabri.

The group has pinned the average temperature of the universe at 2.73 Kelvin – not far above absolute zero – but more impressively, it’s also given a number to the rate at which the universe is cooling: roughly one degree every three billion years.

The cooling is predicted by the big bang theory, CSIRO notes in this press release.

To slip the thermometer under the tongue of the universe, the scientists examined how a galaxy 7.2 billion light years distant affects the radiation received from a pulsar designated PKS 1830-211.

“Radio waves from this quasar come through the gas of the foreground galaxy. As they do so, the gas molecules absorb some of the energy of the radio waves. This leaves a distinctive ‘fingerprint’ on the radio waves”, the CSIRO release explains.

The measurement of the cooling has implications beyond merely validating the big bang, the astronomers explain in their paper (on Arxiv here, and soon to be published in Astronomy & Astrophsyics. It can also help put limits around our investigations of dark energy.

Astronomers from Australia, France, Sweden and Germany took part in the research. ®